Page 1 | 2Influenza (Flu)

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Influenza Resources

Types of Influenza

Avian influenza is caused by avian influenza viruses, which occur naturally among birds.
Pandemic influenza causes a global outbreak, or pandemic, of serious illness that spreads easily from person to person.
Seasonal influenza is a contagious respiratory illness caused by influenza viruses.

For more information about pandemic influenza and Utah's pandemic planning tools, visit Utah's Bureau of Epidemiology's pandemic influenza page.

How Influenza Spreads

Flu viruses are spread through droplets that are created when people with flu cough, sneeze or talk. People who are nearby breathe in these droplets or possibly inhale them into the lungs. Sometimes, a person might also get flu by touching a surface or object that has flu virus on it and then touching their own mouth or nose.

Most healthy adults may be able to infect others beginning one day before symptoms develop and up to five to seven days after becoming sick. Children may pass the virus for longer than seven days. Symptoms start one to four days after the virus enters the body. That means that you may be able to pass on the flu to someone else before you know you are sick, as well as while you are sick. Some persons can be infected with the flu virus but have no symptoms. During this time, those persons may still spread the virus to others.

Influenza Signs & Symptoms

Influenza vaccine is the primary measure to avoid illness from the influenza. However, illness can still occur. The following information may be helpful for those who do get influenza.

1) Be Aware of Common Flu Symptoms

The influenza usually comes on suddenly and may include these symptoms:

  • High fever
  • Headache
  • Tiredness/weakness (can be extreme)
  • Dry cough
  • Sore throat
  • Runny nose
  • Body or muscle aches
  • Diarrhea and vomiting also can occur, but are more common in children.


These symptoms are usually referred to as "flu-like symptoms." Many different illnesses, including the common cold, can have similar symptoms.

2) Cold versus the Influenza

The influenza and the common cold are both respiratory illnesses caused by different viruses. Because these two types of illnesses have similar symptoms, it can be difficult to tell the difference between them. In general, the influenza is worse than the common cold, and symptoms such as fever, body aches, extreme tiredness, and dry cough are more common and intense. Colds are usually milder than the influenza. People with colds are more likely to have a runny or stuffy nose. Colds generally do not result in serious health problems, such as pneumonia, bacterial infections, or hospitalizations.

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